Originally Posted by Unregistered

You normally need to wait an hour before you can reuse a given helper. Being able to use someone repeatedly for the event boss is an abnormality, but not a bug.

It's not an abnormality, there is logic.

I play in a time period where the number of players online is at its lowest, and therefore, my list refreshes more frequently. I've been able to use the same helper multiple times in a row on many occasions, because most people on my friend list are not available during the weeknights (they got there due to me being online earlier on a weekend)